Lopez began feeling tightness in the fifth. His velocity dropped so much in that inning that Phillies pitching coach Rich Dubee and the Citizens Bank Park scoreboard operator both thought that Lopez was throwing changeups. The 82-mph offerings were actually fastballs.
"So far, I don't think it's something bad," said Lopez, who threw 69 pitches and allowed two runs on five hits before being removed. "Good thing for me now that the [All-Star] break is coming. It's going to give me a little more time."
Lopez was feeling better after the game, and no further tests have been scheduled.
The 33-year-old right-hander said that "uncomfortable" was a better adjective than tight or sore.
"Like when the muscles are really, really tired, where it starts to bother you -- that's the way I felt," he said.
It was Lopez's second start of 2009 after a nearly two-year layoff. He had tossed 6 1/3 strong innings of two-run ball Friday against the Mets in his first big league outing since July 26, 2007, and first win since July 7, 2007.
Lopez went 15-9 with a 3.57 ERA in '02, his first full season, finishing second in the American League Rookie of the Year voting. He struggled in '03 after being named the Orioles' Opening Day starter, but went 14-9 with a 3.59 ERA in '04 and reached the 15-win plateau again in '05.
But after an 18-loss season, Lopez was shipped to the Rockies in '07. That summer, he hurt his arm and needed Tommy John elbow ligament replacement surgery, and he had been on the long road back since.
Lopez's previous experience helped him decide to report his injury to manager Charlie Manuel.
"I was smart," Lopez said. "I just don't want to make it worse and put my career in jeopardy."
David Gurian-Peck is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.